The present invention relates to an input device which can input operation signals to host equipment.
Electronic Data Interchanges (commercial dealings) carried out through a network such as the Internet, etc. are carried out by information processing apparatus such as personal computers, mobile telephones or PDAs (Personal Digital Assistants), etc. In Electronic Data Interchanges, in order to realize the safety of dealings, there are instances in which a fingerprint, which is one form of bio-identification information, is collated with fingerprints registered in advance to thereby carry out certification with respect to the opponents in the dealings. This fingerprint collation is carried out by ordinarily connecting a fingerprint collating device to an information processing apparatus.
Moreover, a mouse for specifying an operating position on a computer screen, a keyboard for inputting characters and/or symbols, etc., and a drive unit for loading an external memory device, such as a memory card, etc., are connected to the information processing apparatus as peripheral equipment.
However, since there ordinarily are only several connecting portions for connecting peripheral equipment provided in the information processing apparatus, there are instances where a fingerprint collating unit cannot be newly connected. Further, in order to connect a fingerprint collating device, it is difficult to carry out connection/exchange with respect to peripheral equipment already connected to the information processing apparatus. In addition, the peripheral equipment which has been detached from the information processing apparatus could not be used for that time.
Meanwhile, in general, fingerprint detection methods for realizing the fingerprint collation function include an optical detection method of picking up the image of a fingertip using an image pick-up device, and an electrostatic capacity detection method of forming a capacitor to detect differences in capacitance depending on the fingerprint. Further, in order to connect to the information processing apparatus as a peripheral device, the electrostatic capacity type is advantageous for the purpose of suppressing enlargement of the equipment. In the fingerprint detection method of the electrostatic capacity type, as shown in FIG. 12, a barrier metal 102 consisting of Ti, etc. is formed on a substrate 101 where there are formed elements such as transistors, etc. which constitute a fingerprint sensor 100. At the upper surface of the barrier metal 102, metallic wiring (Al wiring) 103 is formed. A passivation film 105 consisting of silicon nitride film or silicon oxide film is formed at the uppermost layer of the substrate 101.
At the fingerprint sensor 100, as the result of a finger touching the passivation film 105, a capacitor is formed between the Al wiring 103 and the finger. The distance d between each Al wire 103 and the finger changes in accordance with the uneven state of the finger resulting from the fingerprint. Accordingly, at respective capacitors constituting the fingerprint sensor 100, differences in capacitance occur in accordance with individual fingerprints. By detecting such differences, fingerprint recognition can be carried out.
However, when the finger of the user is charged with static electricity, the fingerprint sensor 100 cannot precisely detect differences in the capacitance of the respective capacitors produced by the presence or absence of the fingerprint, thus failing to precisely detect the fingerprint.
Further, when dust, etc. is deposited on the passivation film 105 of the fingerprint sensor 100, it is impossible to precisely detect the differences in capacitance of the respective capacitors, thus failing to precisely detect the fingerprint.
Also, in fingerprint detection by the optical detection method, when dust, etc. is deposited on the image pick-up unit, such as a CCD or line sensor, etc., it is impossible to precisely pick up the image of an upheaval (rising) line of a fingerprint, thus failing to precisely detect the fingerprint.